Method and mechanism for generating gears, racks and the like



16 Sheets-Sheet 1 l In lill ul l u .J

INVENTOR. #M MLZMJJ/U G. ROMI May 14, 1963 METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Filed July 10, 1957 May 14, '1963 f G. RoMl l 3,089,392

METHOD AND MECHANISM FOR GENERATING GEARs, RAcKs AND THE LIKE Filed July 10, 1957 16 Sheets-Sheet 2 INVENToR.

BY WMM METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Filed July 1o, 1957 G. ROMI May 14, 1963 16 Sheets-Sheet 3.

IN VEN TOR. JWM

@Ml/Mw 16 Sheets-Sheet 4 BY MJM May 14, 1963 METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE med July 1o, 1957 May 14, 1963 G. ROMI 3,089,392

METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Filed July 1o, 1957 le sheets-sheet 5 IN V EN TOR.

Maly 14, 1933 G. RON" 3,089,392

METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Filed Julyl 10, 1957 16 Sheets-Shea?I 6 'ff/j. 12

IN V EN TOR.

MMM BY Mga@ May 14, 1963 G. RoMl 3,089,392

METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Filed July 10, 1957 16 Sheets-Sheet 7 IN V EN TOR. Fl 6.11 mD/M G. ROMI May 14, 1963 METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE 16 Sheets-Sheet 8 Filed July l0, 1957 INVENTOR. ,0MM BY mbxm May 14, 1963 G. RoMl 3,089,392

METHOD AND MEcEANIsM Foa GENERATING GEARS, RAcxs AND THE LIKE Filed July 1o, 1957 1e Sheets-sheet 9 sof mi 1N VEN TOR.

fuma BY mum May 14, 1963 G, ROM| METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Filed July l0, 1957 16 Sheets-Sheet l0 6 INVENTOR."'

May 14, .1963 G. RoMl 3,089,392

METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Filed July l0, 1957 16 Sheets-Sheet 11 llllllllllllll l l xl lilllx FIG. 15

METHOD AND MECHANISM FOR GENERATING GEARs, RACKS AND THE LIKE 16 Sheets-Sheet 12 G. ROMl far . IN VEN TOR. www BY MKM FIGJG May 14, 1963 Filed July 10, 1957 G. RoMl 3,089,392

METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE May 14, 1963 16 Sheets-Sheet 13 Filed July 10, 1957 m llllJmv Y INVENTOR. 9m/Www. huhu/0J. M

Tim,

May 14, 1963 G. RoMl 3,089,392

METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Filed July 10, 1957 16 Sheets-Sheet 14 FIG.18

IN V EN TOR.

BY MMM@ May 14, 1963 G. RoMl 3,089,392

METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Filed July l0. 1957 16 Sheets-Sheet 15 Fmg 6.6 |c9o f2 FIG. 200

INVENTOR.

n JMW v BY WJ May 14, 1963 G. RoMl 3,089,392

METHOD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Filed July 1 0, 1957 16 Sheets-Sheet 16 o' r 39 I c I 36 H I INVENToR. www mw FIG. 21 BY )wml/mp United States atent hee 3,089,392 METHD AND MECHANISM FOR GENERATING GEARS, RACKS AND THE LIKE Giordano Remi, Santa Barbara dOeste, Sao Paulo, Brazil Filed .iuly 10, 1957, Ser. No. 671,095 l Ciaims. (Cl. 90-7) The present invention relates to a new method and apparatus for cutting cylindrical gears and racks, by means of the Well known generation method, in which a tooth profile, rolling in synchronism and coupled to a moldable piece, will generate on this moldable piece the exactktooth prole suitable for engagement with itself; in the same way, a gear wheel having a series of tooth profiles with suitable cutting edges generates ou a wheel disc a corresponding series of tooth profiles which will be able to engage with itself, provided that the two wheels are turning in synchronism and that the v gear wheel have reciprocating movements. The profiles of the cutting wheel teeth being involute profiles, in the teeth of the generated wheel there will -be reproduced involute profiles.

The new method, chief object of this invention, which is apparently similar to the conventional ones, and makes use of the properties of the involute curve, is nevertheless, basically diierent from all previously existing methods, because of the type of cutter and machine or machines used, and because of the utilization of the cutting cycle; said cutter and machine or machines when considered as a whole, enable the practical realization of the new method and apparatus for cutting gears and/0r racks in accordance with the invention, as it will be pointed out below in connection with the further objects of the invention.

Another object of the invention is to apply the new method to a new generating gears mechanism which enables the generation of two or more stacks of cylindrical gear wheels with straight or helical teeth, mounted on two different turning shafts with substantial saving of time in the useful cutting cycle.

A further object of the invention is to provide the necessary reciprocating movements in the moulding generation method in such a way that the chief reciprocating movement by means of which the cutting action is performed, is transmitted to a secondary longitudinal reciprocating movement of the turning axis of the cutting gear wheel, by means of which the cutter is alternatively approached and spaced from the piece to be cut.

A still further object of the invention is relative to the fact that when the new method is applied to the new cutting gears mechanism, it is possible to continuously cut the gears, that is to say to cut the gears without stopping the machine; this is due to the fact that it is possible to mount a group of gears to be cut on any one of the two generation stations while on the other generation station is being processed the cutting operation of the other group of gears to be cut. In this way is saved the time for removing and mounting the pieces, normally required in the conventional methods.

Another object of the invention is to allow the use, during the generation operation, of cutting depths and advances substantially heavier than the normally allowable in the conventional methods and machines. This is due to the fact that the new machine has high rigidity conditions because the principle on which it is based enables its construction with -a substantially reduced number of movable members.

A still further object of the invention is related to the fact that without altering the basic conditions of the method it is possible to perform the cutting of racks with the machine used to cut gears; for this purpose it is suflicient to change the rotatory movement of the gear supporting shaft into -a linear movement by means of the application, on said gear supporting shaft, of a suitable device.

A further object of the invention is to apply the iuvented method to a new straight teeth racks generating machine which has absolutely new and original characteristics.

A still further object of the invention is to apply the invented method to a new helicoidal teeth racks generating machine which has also absolutely new and original characteristics.

Another object of the invention is to make the cutter used in the new method as actually consisting of a suitably characterized gear wheel, like a master gear, with envelope prole teeth, which allows to obtain the same results as obtained lby the conventional methods, keeping present the following basic conditions.

For cutting gears:

(l) To create on one or both faces of the gear wheel (cutter)-cutting face or faces-a conical surface which geometric axis is coaxial with the geometric axis of the wheel and having a suitably dimensioned vertex angle. This conical surface is obtained on sharpening the gear wheel (cutter), in such a way that the cutting edges of the teeth are formed by the intersection of saidconical surface with said teeth.

(2) To incline the turning axis of the gear wheel (cutter) through a suitable angle in relation to the turning axis of the gear blank or blanks, and through the same angie in relation to the direction of the main reciprocating movement.

(3) To keep unchanged the inclination angle cited in (2) during the reciprocating action lof the gear wheel (cutter), the turning axis of the gear wheel (cutter) and of the gear Iblank or blanks, being coincidental with a plan which coincides with the main reciprocating movement direction, parallel to the turning axis of the gear blank or blanks, and with the secondary reciprocating movement direction, parallel to the turning axis of the gear wheel (cutter).

F or cutting racks:

(l) T o create on vone face .of the gear wheel (cutter)- cutting face-a conical surface the geometrical axis of which is coincident (coaxial) with the geometrical axis of the wheel, and having a suitably dimensioned vertex angle. This conical surface is formed by sharpening the cutter in such a way that the cutting edges of the teeth of the gear wheel (cutter) are formed by the intersection of said conical surface with said teeth.

(II) To incline the gear wheel (cutter), that is to say to incline all the yplans perpendicular to the turning axis of the gear wheel (cutter) through a suitable angle in relation to .the plan which contains the longitudinal axis of the blank rack at the moment in which this plan coincides with the generation plan.

(lll) The direction of displacement for generating the rack is to be parallel to the intersection of any plan perpendicular to the axis of the gear wheel (cutter) with the generation plan, that is `to say, i-t is to be parallel to the longitudinal axis of the blank rack.

(lV) To impart a reciprocating movement in a direction perpendicular to the longitudinal axis of the rack, Ithis direction making, with the turning axis of the gear `wheel at the generation act the same angle as deiined in (II).

|(V) To keep substantially .constant the inclination angle yof the gear wheel (cutter), as defined in (Il).

A still further object of the present invention is to allow the use of a pattern gear with helicoidal teeth of suitable characteristics as gear wheel (cutter) in the application of the new method, as a result of which helicoidal gears or racks may be generated.

Another object of the present invention is to avoid the use of additional devices required in the conventional methods, in order to obtain some special characteristics; this is `automatically done when the invented method is applied to the new racks generating mechanisms.

Another object of the invention is to provide that by using as cutter a pattern gear wheel of suitable characteristics, and by observing the basic conditions (l), (2), (3), and (I), (II), (III), (IV), (V), it is no more necessary that the flanks of the cutters teeth are formed by involute helicoid surfaces, or like surfaces specially developed as occurs by using the known processes; similarly, it is no more necessary that the heads of the teeth have such an exit angle that their widths, through any plan perpendicular to the turning axis of the cutter are kept approximately constant; it is also no more necessary to keep approximately constant the cutting depth during all the useful life of the cutter, neither is it any longer necessary that the teeth profiles are specially determined and corrected in order to ensure, after each sharpening, cutting characteristics more or less constant.

A still further object of the invention is to allow that the `gear wheel (cutter) works during all its life and even after several sharpening operations always with constant operating or cutting pressure angle, differently from the conventional methods, which are characterized by the fact that they operate with cutting or operating pressure angles which are changed af-ter each sharpening operation.

A still further object of .the invention is to facilitate the construction of the cutter (pattern gear wheel) used in connection with the new method, without using any specially designed equipment, but using only the ordinary standard machinery which is normally employed to cut and rectify precision cylindrical gears.

Another object of the invention is to use the same ideas and the same basic principles in order to create a number of machines intended to be employed for various purposes in the art.

A still further object of the invention is `to obtain that the new method for cutting teeth, applied to new mechanisms, have all the advantages and allow all the applications for gear and racks generations purposes which are actually performed by Athe existing similar machines; besides, the new method may be employed for cutting pieces of various different shapes, always making use of the generation principle.

Other advantages and further objects of the present invention will be evident from the following description, which is made in connection with the appended drawings, land given, both description and drawings, by way of non- -restrictive example.

FIG. 1 is a diagrammatic front view of the new gear generating mechanism;

FIG. 2 is a diagrammatic side view of the new gear generating mechanism;

FIG. 3 is a diagrammatic top view of the new gear generating mechanism;

FIG. 4 is a perspective view of the upper part of the new gear generating mechanism, taken from arrow D of FIG. 2;

FIG. 5 is a section through C-C of FIG. 2;

FIG. 6 is a diagram showing the driving devices for the rotatory movements of the cutter and of the blank gears in the new gear generating mechanism;

FIG. 7 shows diagrammatically the hydraulic device which commands the reciprocating cutting cycle of the new gear generating mechanism, at the end of the upwards main reciprocating movement and at the beginning of the downwards secondary reciprocating movement;

IFIG. 8 is a diagrammatic view of the hydraulic device which commands the reciprocating cutting cycle of the new gear generating mechanism, -at the end of the downwards secondary reciprocating movement and at the beginning of the downwards main reciprocating movement;

FIG. 9 is a diagrammatic view of the hydraulic device which commands the reciprocating cutting cycle of the new gear generating mechanism at the end of the downwards main reciprocating movement and at the beginning of the upwards secondary reciprocating movement, in opposite sense relative to FIG. 8.

FIG. l0 is a diagrammatic view of the hydraulic device which commands the reciprocating cutting cycle of the new gear generating mechanism, at the end of the upwards secondary reciprocating movement and at the beginning of the upwards main reciprocating movement in opposite sense relative to FIG. 9.

FIG. 11 is a diagrammatic view showing the displace ment movement of the head of the new gear generating mechanism;

FIG. 12 is a diagrammatic view showing the relative positions of the gear blanks and of the gear wheel which is used as a cutter;

FIG. 1.3 is a diagrammatic view of the cutting racks device, as applied to the new gear cutting mechanism.

FIGS. 14a and 14C are a side views, and FIGS. l4b and 14d are sectional views taken on line A14b-14I7, and line 14d-Amd, respectively, and illustrating two embodiments of cutters of the present invention.

FIG. 15 is a diagrammatic front view of the new straight teeth racks cutting mechanism.

FIG. 16 is a diagrammatic side view of the new straight teeth racks cutting mechanism.

FIG. 17 diagrammatically shows the application of the new method to a new helicoidal teeth racks cutting mechanism.

FIG. 18 diagrammatically shows the relative positions of the gear wheel (cutter) and of the rack blank, when the new method is applied to the rack cutting mechanism.

FIG. 19 digrammatically shows the relative positions of the gear wheel (cutter) and of the rack blank, at the generation act.

FIG. 19a shows projections of a tooth, and FIG. l9b is a sectional view taken on line P-P in FIG. 19a.

FIG. 20 diagrammatically shows the relative positions of the gear wheel (cutter) and of the piece to be cut, and FIG. 20a shows several projections of a tooth of the gear wheel (cutter) on the generation plane;

FIG. 2l diagrammatically shows the relative positions of the gear wheel (cutter) and of the blank gear at the generation act, with projection of this position on the generation plan G-G.

As represented in FIGURES 1, 2, 3, 4, 5 and 6, the machine for cutting teeth in cylindrical gears to which was applied the new method in accordance with the invention, consists of a body 1, with two parallel vertical guides 2, along which is movable the head 3 of the machine, in both the senses indicated by the arrows Y! and Y2, and in a direction parallel to the longitudinal axis of the vertical guides 2; said body 1 is also provided, at its lower part, which constitutes the base 4 of the machine, with two other horizontal parallel guides 5, which have their longitudinal axis disposed perpendicularly to the plane formed by the vertical guides Z; on these horizontal guides S and in a direction parallel to their longitudinal axis, are movable the blank gear supporting tables 8 and 8a.

Each table 8 and 8a supports the wheel or group of wheels 9 and 9a on which the teeth are to be generated by turning them about their geometric axes Y-Y and Y a-Ya, respectively; these axes are parallel and contained in a plane which is parallel to the plane of the vertical guides 2 and consequently is perpendicular to the plane of the horizontal guides 5. The turning axes Y-Y and Ya-Yu are, consequently, parallel to the direction of displacement of the head 3, indicated by arrows Y1 and Y2.

The head 3 of the machine supports the main shaft .10 to which is xed the cutter 11; the turning axis X-X of this cutter coincides, therefore, with the geometric axis of the shaft 10. The turning axis X-X is coplanar with the turning `axes Y-Y and Y-YL of the wheels 9 and 9a and forms with the axes Y-Y and Ya-Y84 an angle a; consequently the axis X-X forms with the vertical guides 2 and with the direction of displacement of the head 3, which is marked by arrows Y1 and Y2, the same angle ot. This angle oc is kept unchanged during the displacements of the head 3 with the shaft -10 and the cutter 11 along the vertical guides 2.

The displacement of the cutter 11 with the shaft 119 and the head 3 in the senses marked by arrows Y1 and Y2 constitutes the main-or cutting-reciprocating movement of the cutter 11, needed in connection with the molding generation method.

The position of the turning axis X--X of the cutter inclined at an angle a to the turning axes Y-Y and Ya-Y,l of the blank wheels, and consequently, at the same angle a to the direction of displacement marked by arrows Y1 and Y2 is the basic characteristic of the new method and apparatus for cutting gear teeth according to the present invention. As a matter of fact, all the similar conventional methods of generating cylindrical gears with straight or helicoidal teeth, based upon the known principle of molding generation with reciprocally movable circular cutters, require, as fundamental condition, that the turning axes of the cutter and of the gear blank are parallel to each other and to the direction of the main reciprocating movement.

The upper end 10a of the shaft 10, over which is transmittedas will be pointed out laterthe rotatory movement to the cutter (11) has-during the reciprocating movement of the head 3 along the vertical guides 2 in either the senses marked by arrows Y1 and Y2, and as a result of this movement-a horizontal displacement movement respectively in either the senses marked by arrows `6a and 7a (FIGS. 3, 4 and lll). Said upper end @19a is, therefore, supported by the movable slide i12 which has two horizontal guides 13, parallel to each other, and which may be displaced on two corresponding channels .14, the longitudinal axis of which are coplanar with the longitudinal axis of the horizontal guides 5.

On the other hand the shaft 1@ and consequently also the gear cutter 11, fixed to the rst, may move along the turning axis X-X in either the two senses marked by arrows X1 and X2. This movement constitutes the secondary reciprocating movement of the gear cutter 11, in the molding generation process, as will be later explained in detail.

ln order to ensure the free transmission of the rotatory movement of the gear cutter y11, during the displacement of the head -3 in either the two senses marked by arrows Y1-Y2, while the movable slide 12 is moved with its mechanism respectively in either the two senses marked by arrows 6a and 7a, the endless worm screw 32 is provided, which can axially move in either the two senses marked by arrows 6a and ia along the grooved shaft 31 together with the slide 1.?. (FIGS. 3 and 4). Worm screw 32 is mounted on head L12 non-movable in direction 6a, 7a.

With reference now to -FlG. 1l, the reasons of the movement of slide 12. in either the two senses marked by arrows 6a and 7a will be explained.

It is to be noticed that the main cutting reciprocating movement is effected by cutter 111 in the direction shown by arrow M, from point Q to point Q', the distance M between Q and Q Ibeing equal to the distance M1, covered by head 3 in its corresponding movement.

Head 3 moves in the sense of the arrow Y2 during its movement from Q1 to Q5 over the distance M1.

Head 3, going from Q4 to Q5 carries the shaft 1d; having this shaft 10 an inclination angle a with the displacement direction, shown by arrows M1 or Y2, the axis S of it is consequently displaced to S1.

Since fthe worm wheel 33 and shaft 10 are turnably mounted in slide 12, this slide 12 is obviously caused to move lfrom S2 to S3 together with shaft 10 and over a distance which is equal to S-S1 in direction of arrows 6a, 7a.

The movement in the direction of arrows M1 and M lwas downwardly performed by head 3.

When head 3 moves upwardly, from point Q6 to Q7, in the direction of arrows M3 and Y1 carrying the shaft 1t) and its cutter 111, and consequently displacing the cutter from Q2 to Q3, the axis S1 of the shaft -10 returns to its initial position S and--as previously explained-carries the head 12 in the direction of arrow 7a from position 'S3 to position S2.

It is to be noticed that the movements Q4-Q5, Q--Q1 and QS-Q", QZ--Q3 are main reciprocating movements; the secondary movements have been up to now omitted because they do not cause any displacement of slide 12 and shaft 1@ in the direction of arrows 6a and 7a and will be explained later.

Means for driving the rotatory movement of the gear cutter 11 and of the blank gears 9 and 9a are diagrammatically represented in FIG. 6. References therefore will be made to this figure and to the aforesaid FIG- URES 1, 2. and 3. The power of the electric motor is transmitted-over a change speed gear box 16, which allows the work at several speeds-to a shaft 19, to which is xed a bevel gear 17; this bevel gear 17 engages with another bevel gear 18, and thus the movement is transmitted to the mechanism of the slide 12, as explained lbelow. At the same time, the shaft 19 transmits power and rotatory movement to the ibevel gear Ztl, which is coupled to the bevel gear 21; this bevel gear 21 is iixed to the shaft 2.2, by means of which the movement is transmitted to the mechanisms of the tables 8 and 8a, as will Ibe explained below.

As the transmission relationship between gears 17-13 and 2d-211 is 1:1, the horizontal shaft 212 and the vertical shaft 23 will revolve at the same angular speed. The horizontal shaft 22 transmits power and movement tothe gears of the gear Iboxes 24 and 24a lprovided at the base 4 of the machine; these gear boxes retransmit the power and the movement by means of the grooved shafts 25 and 25a to the endless worm screws 26 and 26a which, in turn, further transmit said power and movement to the helicoidal worm gears 27 and 27a; said helicoidal gears are turning about the turning axis Y-Y and Ya--Ya with the shafts 2S and 28a, to which are fixed the gear blanks 9 and 9a. Power and movement are thus transmitted from motor 1S to gear blanks 9 and 9a.

In order to assure that the rotatory movement tothe gear blanks 9 and 9a is transmitted independently of the displacement of tables or carriages 8 and 8a in either of the two senses marked by arrows 6 and 7a, the endless worm screws 26 and 26a are slidably mounted on the `groovecl shafts 25 and 25a.

To the vertical shaft 23 is also iixed the .bevel gear 29, which engages with the bevel gear 29a, iixed to a shaft 29h. t

On the shaft 2gb is xed the bevel ygear 30 engaged with the bevel gear 30a; this -gear Stia transmits power and movement to the grooved shaft 31, on which slides the endless worm screw 32 which meshes with the helical worm gear 33, the turning axis X-X of which forms an angle of (9W- o0 with the axis of worm screw 32. The worm gear 33 is mounted near the upper end 10a of the shaft 1t?, in such a manner that this shaft can slide in both the senses marked by arrows X1 and X2 while receiving from worm gear 33 the transmitted rotatory movement about the axis X-X of the gear cutter v11, which, therefore, turns with the shaft 10.

Since :the transmission of power and of rotatory movement from shaft 19, over 23, 29b, 31 to the shaft 10, to which is xed the gear cutter, is effected in a positive and Xed relationship, shaft and shaft 19 will always turn in the same relationship.

The transmission of power and rotatory movementfrom shaft 19, over shaft 22, shafts of the gear boxes 24 and 24a, and shafts 25 and 25a, to the shafts 28 and 82a on which are fixed the gear blanks 9 and 9zz-is eiected in such a manner that the transmission ratio can be changed. The changes in the transmission ratio between shaft 19 and shafts 28 and 28a are carried out by means of the gear boxes 24 and 24a. The changes in the transmission ratio allow-within the limits of the machines capacity-the synchronization of a great number of gear blanks ywith quite different members of teeth to be cutwith the gear cutter 11.

`In fact, on cutting a given gear with n teeth by means of a gear cutter with 111 teeth, it will be suicient to multiply the relation 111:11 by the machine relationship, to find the corresponding gears and to put them into the gear boxes 24 or 24a. The manner in which these gear ratios can be found is well known and does not constitute an object of the present invention. The machine, therefore, allows to mold at the same time gear blanks 9 and 9a with the same or with different numbers of teeth.

Hydraulic control means are provided to permit operation at the various possible different speeds and strokes of the main reciprocating movement of the head 3 and of the gear cutter 11 in either the two senses marked by arrows Y1 and Y2, and at operators choice in accordance with specific requirements with secondary reciprocating movement of the gear cutter in either the two senses marked by `arrows X1 and X2. The hydraulic control means control the movements of the carriages `t; and 8a in either the two senses marked yby arrows 6 and 7; and inally are capable to slowly move for adjustment purposes the head 3 in either lthe two senses marked by arrows Y1 and Y2. The construction of the hydraulic system is not part of this invenn'on.

The suitable synchronization of the main and secondary reciprocating movements is also performed by means of the hydraulic system the construction of which does not form part of the present invention, and this synchronization will be explained below.

The hydraulic control system for operation and synchronization of the reciprocating movements of the head 3 and of the shaft 10 will be now described with reference to the FIGURES 7, 8, 9, l() of the drawings.

The hydraulic control system consists of A valve 101, for reversing the main and secondary reciprocating movements. A stationary piston 1102, xed to the body 1 of the machine. A piston 103, fixed on the shaft 10 which can move in either the two directions X1 and X2 (secondary reciprocating movement). The head 3 of the machine, which moves in the directions Y1 yand Y2 (main reciprocating movement). The check valves 104 and 105 which allow the oil to pass only in the directions marked by the arrows 106 and 107 respectively.

To operate the head 3, the oil can enter alternatively through openings 110 and 111.

To operate the piston 103 the oil can enter alternatively through openings 108 and 109.

The valve 101 consists of a piston 117 which can be axially moved, said valve 101 having an oil inlet 119 through which the oil is fed under pressure by means of a pump (not represented in the drawings), two oil outlets 120 and 121 for discharging purposes, and two openings 122 and 123 which, depending upon the position of the piston 117, can serve as an oil inlet from the pump (see FIG. 7) to the chambers 124-126 and as an oil outlet from the chambers 128-127 (as represented in FIG. 7) or, alternatively (see FIG. 8) as an oil outlet from the chambers 124-'126 and as an oil inlet to the chambers 12S-127.

The piston 117 is operated by means of the lever 112, which bears on point 113 and can move in the senses marked -by arrows 114e and 114b.

rThe lever 112 is operated by means of the stop latches 115 and 116 tixed to the head 3 and which can be mounted in different positions in order to regulate the head run in the main reciprocating movement. Reversing the main reciprocating movement `is effected when any one of the stop latches 115 or 116 abuts the end 112a of the lever 112, during the movement of the head 3 in either the two senses Y1 and Y2.

Let us assume that the head 3 of the new gear generating machine is near the end of the main upward reciprocating movement and beginning of the secondary downwards reciprocating movement, as `diagramrnatically represented in FIG. 7.

As shown by the arrows, the oil enters through pipe 119 into the annular chamber 140 and through the outlet 122, after passing through passage 109, enters the annular chamber 124 which is part of the cylindrical housing of piston 103 associated with the secondary reciprocating movement.

From chamber 124 the oil can pass to the annular chamber 126 through passages 125 and 110. As indicated by the arrows, from chamber 127, which is the lower part of the cylindrical housing of the main reciprocating movement, the oil goes out through passage 111, passes freely through valve 104, enters the chamber 141 through the passage 123 and is discharged through pipe 121. As also indicated by the arrows, the oil is discharged from chamber 128 through passage 108, passage 123, chamber 141 and pipe 121.

The Astop latch 115 abuts the end 112a of the lever 112 and as a result of the movement of head 3 in the direction of the arrow Y1 due to the oil pressure exerted on `face 126e of piston 102 within the chamber 126, will lift said lever, as will be explained in connection with FIG. 8.

In FIG. 8 the head 3 is in its extreme ascending position and having the stop latch cooperated with the end 112a of lever 112, has lifted this one in the direction of arrow 114a.

The lever 112 on moving in the cited direction has carried the piston 117 as a result of which the oil ow is changed lfrom the passage 122 to the passage 123, as indicated by the arrows.

Through passage 123, as indicated `by the arrows, and through inlet 10S, the oil reaches the chamber 128, displacing the piston 103 to which is xed the shaft 10 and gear cutter 11 a distance D, until the face 124a of piston 103 abuts the face 124b of the cylindrical housing. During its travel, the piston 103 opens the passage 129, through which the oil can enter the chamber 127, after having passed through passage 111. From chamber 124, as indicated by the arrows, the oil passes through passage 109 and is discharged through passage 122, valve 101 and pipe 120. From chamber 126, as indicated by the arrows, the oil passes through passage 110, passes freely through valve 105 and is discharged through passage 122, chamber 141a, valve 101 and pipe 120.

The main downwards reciprocating movement begins with the oil pressure exerted on faces 127a and 127b.

Hence the head 3 moves in the direction of arrow Y2 (see FIG. 9) until the stop latch 116 abuts the end 112a of lever 112, causing the displacement of piston 117 and thus initiating the reversion of said displacement.

The stop latch 116, abutting the end 112e of lever 112, causes the lever 112 to move in the direction of arrow 114b. Lever 112 carries the piston 117 and enables the oil to go out from chamber through passage 122, as represented in FIG. 10.

The oil tlowing through passage 122 reaches passage 109 and enters the chamber 124, thus initiating the secondary upwards reciprocating movement. The oil pressure on the faces 124a and 124 causes the piston 103 to rise until its face 123:1 abuts face 128i); the oil can now 

1. GEAR CUTTING MACHINE COMPRISING, IN COMBINATION, FIRST SUPPORT MEANS, AND SECOND SUPPORT MEANS, ONE OF SAID SUPPORT MEANS BEING MOVABLE IN ONE DIRECTION RELATIVE TO THE OTHER OF SAID SUPPORT MEANS; AT LEAST ONE ROTARY HOLDER MEANS FOR HOLDING AT LEAST ONE GEAR BLANK, AND BEING MOUNTED ON SAID FIRST SUPPORT MEANS FOR ROTATION ABOUT A FIRST AXIS PARALLEL TO SAID DIRECTION; ROTARY CUTTER GEAR MEANS HAVING A SECOND AXIS OF ROTATION INCLINED AT AN ACUTE ANGLE TO SAID FIRST AXIS, SAID ROTARY 